Method and systems for isolation and/or separation of products from production processes

ABSTRACT

The present invention relates to separation of desired target products from biological, plant, and waste-type material, wherein the desired target products include renewable fuels such as ethanol, biobutanol, and biodiesel, wherein the separation is conducted with a cross-flow filtration system having the ability to separate desired products from both non-viscous and viscous medium.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of co-pending U.S. patentapplication Ser. No. 15/922,360, filed on Mar. 15, 2018, now U.S. Pat.No. ______, which is a divisional of Ser. No. 14/867,084, filed on Sep.28, 2015, now U.S. Pat. No. 9,937469 issued on Apr. 10, 2018, which is acontinuation of U.S. patent application Ser. No. 13/985,367, filed onOct. 30, 2013, now U.S. Pat. No. 9,163,265 issued on Oct. 20, 2015,which in turn claims priority to PCT Application No. PCT/US2012/025874filed on Feb. 21, 2012 which in turn claims priority to U.S. ProvisionalApplication No. 61/445,010 filed on Feb. 21, 2011, the contents of allof which are incorporated by reference herein for all purposes.

BACKGROUND OF THE INVENTION Field of Invention

The present invention relates to separation of desired target productsfrom numerous hydrocarbon containing materials, including biologicalproducts produced by cells, insects and/or microorganism in a culturemedium; and fuels, such as ethanol, biobutanol, propanol and biodieselfrom multiple sources including biological biomass, plant biomass, wastematter including cellulose materials, etc., wherein the separation ofthe desired target products is conducted with a cross-flow filtrationsystem having the ability to the separate desired target products fromboth viscous and non-viscous medium.

Related Art in Technical Field

Throughout the world more and more companies are looking to recovervalue added products from a wide variety of starting materials thatinclude hydrocarbons, such as plants, roots, root crops, grains,flowers, animal tissue, cell cultures comprising yeast, algal, bacteria,or fungi species, milk, milk products, fruits and fruit juices. Severalbiofuel routes have been pursued including: gasification of biomass tobiogas, pyrolysis of biomass to oils, direct liquefaction, conversion ofplant oils to biodiesel and release of sugars for fermentation toethanol. Further, companies are looking to extract value added productsfrom solid and liquid waste streams such as mill and grain wash waters,fermentation bio-mass and manure. One such waste stream includes biomassfrom bio-fuel production which, during the process and after productionof fuels such as diesel and alcohol, is rich in plant proteins, sugars,oils and carbohydrates. Another such waste stream is cellular biomassused for protein and essential fatty acids production from wild and/orrecombinant yeast, algae, bacteria, larvae or fungi species.

The production of materials in biotechnology and renewal energy involvesthe isolation, separation, and/or purification of a specific targetmolecule that is surrounded by many other biological components. It doesnot matter whether the material comes from fermentation processes oryard waste, the material of interest must be collected in a reasonablypure form.

The culturing of microorganisms, insect larvae, microbial cells(fermentation) or animal and plant cells (tissue culture) are central toa multiplicity of commercially-important chemical and biochemicalproduction processes. Microorganisms, insect larvae and living cells areemployed in these processes as a result of the fact that all caneconomically synthesize commercially-valuable chemicals. The desiredproduct(s) can be either purified from the liquid medium or extractedfrom the cells themselves.

Biofuels, such as ethanol or biobutanol have widespread application asindustrial chemical, gasoline additive or straight liquid fuel. As afuel or fuel additive, both ethanol and biobutanol dramatically reducesair emissions while improving engine performance. As a renewable fuel,they reduce national dependence on finite and largely foreign fossilfuel sources while decreasing the net accumulation of carbon dioxide inthe atmosphere. Such biofuels can be produced by multiple sourcesincluding microorganisms or derived from other materials that includescomponents such as cellulose, hemicellulose, lignin, protein andcarbohydrates such as starch and sugar. Ethanol typically has beenproduced from sugars derived from feedstocks high in starches andsugars, such as corn. Recently, other forms including biomass frommicroorganisms, trees, shrubs and grasses, corn and corn husks, animalwaste including manure, as well as municipal solid waste, waste paperand yard waste have been used in the production or isolation of ethanoland biobutanol.

The basic steps of biofuel production from cellulose include hydrolysisof biomass to sugars and then subsequent fermentation of sugars toethanol. However, there are several places in the process where thereare bottlenecks for efficient production of ethanol from these lessexpensive cellulosic wastes. Specifically, these bottlenecks includeinhibitory effect of ethanol on microorganisms (inhibition due tochanges in fluidity of biological membranes) and limitations on flowrate for continuous process because of the viscosity or bulk of theliquid medium. One approach to process improvement would be using acontinuous fermentation integrating an ethanol removing/recoveryoperation, thereby maintaining the ethanol concentration in thefermentation broth at a level which is minimally inhibitory tofermenting organisms.

Attempts to address the issue of high feedstock prices have included useof less expensive feed stocks. Cellulosic biomass (agriculturalwaste/residue etc.) can be used for conversion to ethanol as a lessexpensive feedstock alternative to corn. However, it has been found thatbiomass and cell cultures that include highly viscous materials are farmore difficult to process, such that, even though the cell culture isfive (5) times denser the yield of final product is only 50% greaterbecause the viscosity of the material prevents the separation of thedesired target molecule from the mass of cellular materials. In the caseof extracts of solid phase material, such as plants and animal tissue,the problem is the same such that the viscous materials clog filters andblock chromatography columns as well as not separating efficiently undernormal centrifugal forces.

Although it would appear that a simple dilution of the viscous materialwould solve the problem, this creates at least four additionalproblems: 1) the cost of the diluent which can be highly expensive inthe case of diluents for pharmaceutical intended for human injection, 2)disposal of the higher volume of the waste stream, i.e. the originalvolume plus the volume of diluent, 3) the cost of the necessary tanksand mixing equipment in order to dilute the starting material, and 4)additional purification costs for the diluted final product.

Thus, when the starting mixture is very complex, isolation of thematerial of interest can be especially difficult and often requirescostly operations. Technologies that reduce the number of separationoperations and simplify recovery procedures are in high demand inbiotechnology and several other industries including water treatment,ethanol production, food and beverage, and chemicals. As such, there isa need for an improved and less costly separation system that issuitable for large-scale isolation of components of interest from acomplex and/or viscous sample.

SUMMARY OF THE INVENTION

The present invention relates to the production and separation processesof a target molecule from hydrocarbon containing materials, such as,biomass, sugarcane bagasse, rice hulls, corn, corn stover, wheat straw,rice straw, sugar beet pulp, citrus pulp, citrus peels, hardwoodthinnings, softwood thinnings, wood chips, sawdust, pulp mill waste,urban paper waste, grass clippings, switchgrass, hybrid poplar wood,miscanthus, fiber cane, fiber sorghum, animal manure, etc.

In one aspect, the present invention provides for a separation method ofat least one target molecule from hydrocarbon containing material, themethod comprising the steps of:

-   -   providing a liquid medium in a vessel wherein the liquid source        medium comprises the at least one target molecule, wherein the        target molecule is selected from the group consisting of        ethanol, biobutanol, proteins, enzymes, sugars, starches, short        or long chain fatty acids, energy containing hydrocarbons and        serum components;    -   providing at least one cross-flow filtration cassette        comprising:        -   an array of sheet members of generally rectangular and            generally planar shape with main top and bottom surfaces,            wherein the sheet members include in sequence in said array            a first retentate sheet, a first filter sheet, a permeate            sheet, a second filter sheet, and a second retentate sheet,            wherein the liquid medium to be filtered flows across the            filter sheets, solids or high-molecular-weight species of            diameter larger than the filter sheet's pore size, are            retained in the retentate flow, and at least a portion of            the liquid medium with any permeate species diffuse through            the filter sheets and enter the permeate sheet and permeate            flow; wherein each of the sheet members in said array has at            least one inlet basin opening at one end thereof, and at            least one outlet basin opening at an opposite end thereof,            with permeate passage openings at longitudinal side margin            portions of the sheet members, wherein each of the first and            second retentate sheets having a multiplicity of channel            openings therein, extending longitudinally between the inlet            and outlet basin openings of the sheets in the array, and            being bonded to an adjacent filter sheet about peripheral            end and side portions thereof, with their basin openings and            permeate passage openings in register with one another and            the permeate passage openings of each of the retentate            sheets being circumscribingly bonded to the adjacent filter            sheet, and with a central portion of each of the retentate            sheets and adjacent filter sheets being unbonded to permit            permeate contacting the retentate sheet to flow through the            filter sheet to the permeate sheet;    -   effectuating a sufficient flow of the liquid medium comprising        the target molecule from the vessel through at least one        cross-flow filtration cassette; and    -   sequentially capturing one or more filtration fractions        generated by the cross-flow filtration modules, wherein the        target molecule is physically separated by said one or more        cross-flow filtration and wherein said physical separation of        target product is based on their different molecular weights,        size and/or operating conditions.

Notably, the liquid medium comprising the target product can bepretreated to remove any unwanted material or larger solids from theliquid medium before introduction into the cross-flow filtrationcassette, wherein the pretreating includes systems such as centrifuge,vibrating screen, mesh screening, belt filter, screw press, hydrocylconeand other systems that may further reduce particle size and/or removeunwanted large material to ensure easy flow through the cross-flowfiltration cassette of the present invention.

Another aspect of the present invention provides for a method ofseparating a renewable fuel molecule from a viscous source material, themethod comprising:

-   -   contacting the viscous source material with a diluent in an        amount sufficient to reduce the viscosity of the source material        and form a continuous stream of diluted viscous source material,        wherein the diluent is contained in a separated vessel from the        viscous source material;    -   flowing the diluted source material into a recirculation loop of        a first cross-flow filtration cassette, wherein the cross-flow        filtration cassette comprises:        -   an array of sheet members of generally rectangular and            generally planar shape with main top and bottom surfaces,            wherein the sheet members include in sequence in said array            a first retentate sheet, a first filter sheet, a permeate            sheet, a second filter sheet, and a second retentate sheet,            wherein each of the sheet members in said array has at least            one inlet basin opening at one end thereof, and at least one            outlet basin opening at an opposite end thereof, with            permeate passage openings at longitudinal side margin            portions of the sheet members, wherein each of the first and            second retentate sheets having a multiplicity of channel            openings therein, extending longitudinally between the inlet            and outlet basin openings of the sheets in the array, and            being bonded to an adjacent filter sheet about peripheral            end and side portions thereof, with their basin openings and            permeate passage openings in register with one another and            the permeate passage openings of each of the retentate            sheets being circumscribingly bonded to the adjacent filter            sheet, and with a central portion of each of the retentate            sheets and adjacent filter sheets being unbonded to permit            permeate contacting the retentate sheet to flow through the            filter sheet to the permeate sheet;    -   diafiltering the diluted source material with sufficient        diafiltration buffer so as to recover the desired yield of the        renewable fuel molecule by passing the renewable fuel molecule        into the first permeate fluid;    -   flowing the first permeate fluid containing the renewable fuel        molecule to a end product vessel;    -   flowing out the first retentate solution from the recirculating        liquid of the first cross-flow filtration cassette into a second        cross-flow filter unit, wherein the flow rate of the first        retentate solution is at the same flow rate as the diluted        source material being fed into the recirculation loop of the        first cross-flow filter apparatus;    -   diafiltering the flow of retentate into the second cross-flow        filter unit with sufficient diafiltration buffer so as to        recover the desired yield of the renewable fuel molecule by        passing the renewable fuel molecule into the second permeate        fluid;    -   flowing the second permeate fluid containing the renewable fuel        molecule to the end product vessel;    -   concentrating the first and second retentate fluid by flowing        same to a third cross-flow filter apparatus communicatively        connected with the second cross-flow filter unit, wherein the        volume of the third retentate fluid is reduced to the        approximate volume of the undiluted source material or less        thereby forming a waste stream for further use;    -   recirculating the third permeate fluid back to the diluent        vessel for reuse;    -   concentrating the first and second permeate fluid by flowing        same to a fourth cross-flow filter apparatus communicatively        connected to the end product vessel wherein renewable fuel        molecule is concentrated and diafiltration buffer is removed in        fourth permeate stream and recirculated for reuse.

In some embodiments, the source material may have a viscosity from about100 cP to about 100,000 cP and in some instances from about 10,000 cP toabout 50,000 cP and the target molecule can still be effectivelyseparated.

In yet another aspect, the present invention provides for a method ofseparating and recovering target molecules from biomass, wherein thebiomass includes fermentation microorganism selected from fungi,bacteria, yeast, mold, microalgae, and macroalgae, the methodcomprising:

-   -   providing biomass from a fermentation, culture or waste stream        and optionally diluting with a diluent to reduce viscosity of        the biomass:    -   providing at least one cross-flow filtration cassette        comprising:        -   an array of sheet members of generally rectangular and            generally planar shape with main top and bottom surfaces,            wherein the sheet members include in sequence in said array            a first retentate sheet, a first filter sheet, a permeate            sheet, a second filter sheet, and a second retentate sheet,            wherein the liquid medium to be filtered flows across the            filter sheets, solids or high-molecular-weight species of            diameter larger than the filter sheet's pore size, are            retained in the retentate flow, and at least a portion of            the liquid medium with any permeate species diffuse through            the filter sheets and enter the permeate sheet and permeate            flow; wherein each of the sheet members in said array has at            least one inlet basin opening at one end thereof, and at            least one outlet basin opening at an opposite end thereof,            with permeate passage openings at longitudinal side margin            portions of the sheet members, wherein each of the first and            second retentate sheets having a multiplicity of channel            openings therein, extending longitudinally between the inlet            and outlet basin openings of the sheets in the array, and            being bonded to an adjacent filter sheet about peripheral            end and side portions thereof, with their basin openings and            permeate passage openings in register with one another and            the permeate passage openings of each of the retentate            sheets being circumscribingly bonded to the adjacent filter            sheet, and with a central portion of each of the retentate            sheets and adjacent filter sheets being unbonded to permit            permeate contacting the retentate sheet to flow through the            filter sheet to the permeate sheet;    -   effectuating a sufficient flow of liquid comprising the biomass        and target molecules from the waste stream through the at least        one cross-flow filtration cassette, using one or more fluid        delivery means, such as pump, wherein each fluid delivery means        is connected to at least one cross-flow filtration module; and    -   sequentially capturing one or more filtration fractions        generated by the cross-flow filtration cassettes, wherein the        target product is physically separated by said one or more        cross-flow filtration cassette and wherein said physical        separation of target product by the at least one cross-flow        filtration cassette is based on their different molecular        weights and/or operating conditions.

The biomass may include cellulosic material selected from the groupconsisting of sugarcane bagasse, rice hulls, corn stover, wheat straw,rice straw, sugar beet pulp, citrus pulp, citrus peels, hardwoodthinnings, softwood thinnings, wood chips, sawdust, pulp mill waste,urban paper waste, grass clippings, switchgrass, hybrid poplar wood,miscanthus, fiber cane, fiber sorghum, animal manure and similarcellulose containing materials.

In a further aspect, the present invention provides for a method ofproducing renewable diesel fuel, comprising:

-   -   culturing a population of a microorganism selected from a        microalgae, an oleaginous yeast or a fungus, in the presence of        a fixed carbon source, wherein: (i) the microorganisms        accumulate at least 10% of their dry cell weight as lipid;        and (ii) the fixed carbon source is selected from the group        consisting of glycerol, depolymerized cellulosic material,        sucrose, molasses, glucose, arabinose, galactose, xylose,        fructose, arabinose, mannose, acetate, and any combination of        the foregoing;    -   isolating lipid components from the cultured microorganisms by        using a cross-flow filtration cassette, comprising        -   an array of sheet members of generally rectangular and            generally planar shape with main top and bottom surfaces,            wherein the sheet members include in sequence in said array            a first retentate sheet, a first filter sheet, a permeate            sheet, a second filter sheet, and a second retentate sheet,            wherein the liquid medium to be filtered flows across the            filter sheets, solids or high-molecular-weight species of            diameter larger than the filter sheet's pore size, are            retained in the retentate flow, and the at least a portion            of the liquid medium with any permeate species diffuse            through the filter sheets and enter the permeate sheet and            permeate flow; wherein each of the sheet members in said            array has at least one inlet basin opening at one end            thereof, and at least one outlet basin opening at an            opposite end thereof, with permeate passage openings at            longitudinal side margin portions of the sheet members,            wherein each of the first and second retentate sheets having            a multiplicity of channel openings therein, extending            longitudinally between the inlet and outlet basin openings            of the sheets in the array, and being bonded to an adjacent            filter sheet about peripheral end and side portions thereof,            with their basin openings and permeate passage openings in            register with one another and the permeate passage openings            of each of the retentate sheets being circumscribingly            bonded to the adjacent filter sheet, and with a central            portion of each of the retentate sheets and adjacent filter            sheets being unbonded to permit permeate contacting the            retentate sheet to flow through the filter sheet to the            permeate sheet;    -   subjecting the isolated lipid components to one or more chemical        reactions to generate straight chain alkanes, whereby renewable        diesel is produced.

In another aspect, the present invention provides for a method ofproducing a renewable fuel molecule from corn, the method comprising:

-   -   providing corn and introducing same into a particle reduction        system to provide a mixture of corn particles with essentially        the same size particles;    -   introducing the corn particles to liquification tank, under        heat, to break apart the starch granules;    -   introducing enzymes for break down of the starch granules into        simple sugars;    -   introducing the simple sugars into a reaction vessel along with        yeast or enzymes for conversion of the simple sugar to ethanol        in a reaction medium;    -   moving the reaction medium into a distillation column for        extraction of the ethanol from the reaction medium; and    -   moving the remaining reaction medium with residual water and        corn solids through a cross-flow filtration cassette of the        present invention, wherein a significant amount of water is        removed and the remaining syrup can be used as a component of        animal feed.

In yet another aspect the present invention provides a method forseparating components from corn, the method comprising:

-   -   providing corn particles, wherein the corn particles are        separated from cobs and foreign material;    -   introducing the corn particles to an acidic medium, under heat,        thereby releasing starch from the corn particles;    -   separating the released starch from the corn particles and        acidic medium by moving the corn particles and acidic medium        through a cross-flow filtration cassette of the present        invention thereby forming a permeate comprising the released        starch and a retentate comprising the corn particles; and    -   combining the released starch with at least one saccharifying        enzyme for conversion into sugars.

Sugars may include a mixture of hexose and pentose sugars, such as,glucose, xylose, arabinose, maltose and galactose.

The saccharifying enzymes may include α-amylase that can hydrolyzestarch, glycogen and α-1.4 glucosidic linkages in its degradatedmaterial, to rapidly reduce the viscosity of colloidal starch solution,produce soluble dextrin and oligosaccharide, and even small amount ofglucose and maltose. Glucoamylase (α-1.4-Glucanglucohydrolase), canhydrolyze α-1.4 glucosidic linkages to produce glucose from thenonreductive end, and can slowly hydrolyze α-1.6 glucosidic linkagesinto glucose. Other applicable enzymes may include pullulanase andβ-amylase.

Additionally, if the starting material is heavily weighted towardcellulose or hemicellulose then additional or different saccharifyingenzymes may be necessary for conversions to desired sugars such as forcellulose into glucose, the enzmes may include endoglucanase or EG;cellobiohydrolases (CBHs), such as (i) CBHI and (ii) CBHII; andBetaglucosidase or BG. For hemicellulose, Beta-xylosidase and Beta1,4-beta-xylanasemay be used for conversion to xylose.

In another embodiment, the remaining corn particles in the acidic mediumcan be treated for separation of targets products such as releasing thewhole germ from the corn particles before the degerminated cornparticles proceed to the saccharification process. Specifically, theseparation method comprises:

-   -   grinding the corn particles to release the whole germ from the        corn kernel;    -   isolating the whole germ from the corn particles; and    -   extracting corn oil from the isolated whole germ.

In still another aspect, the present invention provides for a method ofproducing a renewable biofuel molecule, the method comprising:

-   -   providing a bioreactor system comprising a fermentation tank and        separation filtration cassette communicatively connected to the        fermentation tank, wherein the fermentation tank holds biomass        and any produced renewable fuel molecule, wherein the separation        filtration cassette comprises a multiplicity of filter sheets in        an operative stacked arrangement, wherein the filter sheets        alternate with permeate and retentate sheets, wherein a liquid        to be filtered flows across the filter sheets and solids or        high-molecular-weight species of diameter larger than the filter        sheet's pore size, are retained in the retentate flow, and the        liquid along with any permeate species diffuse through the        filter sheets and enter the permeate sheet and permeate flow; at        least one permeate collection vessel, a retentate inlet and a        retentate outlet in fluid communication with at least a first        and second retentate sheet, where in the retentate sheets        comprise multiple fluid-flow sub-channels each extending between        the feed inlet and retentate outlet that are of equal length to        one another as measured between the inlet and the outlet;        introducing the biomass to the fermentation tank and culturing        the biomass in a fermentation step conducted under conditions to        produce the renewable biofuel molecule;        flowing at least the fermentation liquid medium and renewable        biofuel molecule from the fermentation tank to the separation        filtration cassette; and        capturing the renewable biofuel molecule generated by the        separation filtration cassette.

Yet another aspect of the present invention relates to a method ofcontinuously fermenting and separating a desired renewable fuelincluding a biomass and reactive microorganisms to convert the biomassinto a renewable fuel comprising the steps of:

-   -   providing at least a first reactor vessel wherein the reactor        vessel comprises the biomass and reactive microorganisms useful        in converting the biomass into a renewable fuel;    -   locating a cross-flow filtration system downstream from the        first reactor vessel and configured to receive at least a        portion of the biomass to separate into at least a first        retentate and a first permeate, wherein the reactive        microorganisms are generally retained in the retentate by the        cross-flow filtration cassette and returned to the first reactor        vessel; and    -   isolating the renewable fuel from the permeate.

In a further aspect, the present invention provides for a system forconverting cellulose and/or sugar containing source material such asgarden waste, farm waste, plant waste to energy containing molecules,the system comprising:

-   -   at least one colloid or hammer mill for reducing the particle        size of cellulose and/or sugar containing source material to        produce an emulsified or homogenized source material;    -   at least one fermentation unit in fluid communication with the        colloid or hammer mill for accepting the emulsified or        homogenized source material;    -   at least one cross-flow filtration cassette in fluid        communication with the fermentation unit for separating the        energy containing molecules from the source material, wherein        the cross-flow filtration cassette comprises a multiplicity of        filter sheets in an operative stacked arrangement, wherein the        filter sheets alternate with permeate and retentate sheets,        wherein a liquid to be filtered flows across the filter sheets        and solids or high-molecular-weight species of diameter larger        than the filter sheet's pore size, are retained in the retentate        flow, and the liquid along with any permeate species diffuse        through the filter sheets and enter the permeate sheet and        permeate flow; at least one permeate collection vessel, a        retentate inlet and a retentate outlet in fluid communication        with at least a first and second retentate sheet, where in the        retentate sheets comprise multiple fluid-flow sub-channels each        extending between the feed inlet and retentate outlet that are        of equal length to one another as measured between the inlet and        the outlet; and    -   at least one collection vessel in fluid communication with the        cross-flow filtration cassette for holding the separated energy        containing molecules.

Yet another aspect of the present invention provides for a method forincreasing concentration of thin stillage removed from an ethanolproduction system, the method comprising:

-   -   moving the thin stillage through a cross-flow filtration        cassette of the present invention to provide a liquid containing        at least 30% solids and wherein water removed from the stillage        is reused in the ethanol production system.

In a still further aspect, the present invention provides for separationof products and chemicals involved in a chemical pretreatment ofcellulose biomass. Chemical pretreatment is important in the overallconversion scheme from the choice of biomass to the size reduction,hydrolysis, fermentation and the recovery of biofuel product and otherco-products. Chemical pretreatment includes using any of dilute acid,sulfur dioxide, ammonia and lime (Ca(OH)₂). However, using thesechemical pretreatments may provide a fermentable product but the choiceof chemical should not present processing or disposal challenge of anyformed products. Lime is used for pretreatment because it removes ligninand acetyl groups that have been known to affect hydrolysis rates.However, use of lime produces waste products such as gypsum which isgenerated during the pH adjustment and conditioning of hydrolyzates frompretreatment prior to enzymatic hydrolysis and fermentation. Thus, theseparation of any generated gypsum is necessary and can be easilyremoved by use of the systems of the present invention by placing across-flow filtration cassette between the pretreatment vessel and thatof the container used for enzymatic hydrolysis. The gypsum containingmedia is often very viscous, however, using the cross-flow filtrationcassette of the present invention retains the gypsum while allowing thesugar pass through the membrane.

Another aspect provides for preparation of polymers obtained fromagro-resources such as polysaccharides to replace conventional plasticmaterials. To obtain a thermoplastic material, cellulose, lignins,lignin-cellulose and other starch containing material are used in theprocess. Separation of microfibrils materials from the polysaccharidecontaining material provides for polymeric type material for furtherconversion to polymers. The present invention provides for separationwith the cross-flow filtration cassettes, to isolate the monocrystalsfor further development of the polymeric material.

Other aspects and advantages of the invention will be more fullyapparent from the ensuing disclosure and appended claims.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows the components of a cross-flow filtration cassette used inthe separation of renewable fuels

FIG. 2 shows the flow pattern of the retentate through a multiplicity ofsheets adapted to end plates with retentate inlet and outlet andpermeate inlet and outlet.

FIG. 3 shows a system for fermentation and separation of a desiredtarget.

FIG. 4 shows a system that includes the addition of a particle reductionsystem to ensure optimal particle size for extraction of desiredhydrocarbon molecules.

FIG. 5 shows stages of grinding of a source material, such as grains orbiomass, and movement of same to a liquification tank wherein liquefyingchemicals can be added for treatment of the source material for furtherseparation of proteins and lignins from the source material andsubsequent movement of the source material to a fermentation vessel.

FIG. 6 shows an alternative set up for use of the cross-flow filtrationcassette with multiple fermentation vessels in the separation of ethanoland the res use of yeast.

FIG. 7 shows a set-up for fermentation of a liquid that is devoid ofsolids.

FIG. 8 shows the difference between stillage concentrations by themethod of the present invention relative to that of evaporation.

FIG. 9 shows a simplified flowsheet for ethanol production fromlignocellulosic biomass including some of the possible placements of across-flow filtration cassette of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

While not to be construed as limiting, the terms used herein have thefollowing definitions unless indicated otherwise.

The term “biomass” refers to any material that includes cellulosic orlignocellulosic materials; cellulose, hemicellulose, lignin, starch,proteins, lipids, oligosaccharides, polysaccharide and/ormonosaccharides. According to the present method, biomass may be derivedfrom a single source, or biomass can comprise a mixture derived frommore than one source; for example, biomass could comprise a mixture ofcorn cobs and corn stover, or a mixture of grass and leaves. Biomass mayinclude, but is not limited to, bioenergy crops, agricultural residues,municipal solid waste, industrial solid waste, sludge from papermanufacture, yard waste, wood and forestry waste. Examples of biomassinclude, but are not limited to, corn grain, corn cobs, crop residuessuch as corn husks, corn stover, grasses, wheat, wheat straw, barley,barley straw, hay, rice straw, switchgrass, waste paper, sugar canebagasse, sorghum, soy, components obtained from processing of grains,trees, branches, roots, leaves, wood chips, sawdust, shrubs and bushes,vegetables, fruits, flowers, animal manure and municipal waste.

The term “byproducts” refers to any and all materials produced during orremaining after the separation of the desired target molecule from thehydrocarbon containing material.

The term “conversion” refers to any biological, chemical and/orbio-chemical activity which produces biofuels and byproducts from thehydrocarbon containing material, such as biomass or blended biomass.Such conversion may include any one of the following processes includinghydrolysis, fermentation, and simultaneous saccharification andfermentation (SSF) processes.

The term “deleterious materials” refers to any organic or inorganicmaterial which has the ability to degrade or limit fermentationmaterials or hydrolysis materials in any manner, including theprevention or retardation of the hydrolysis conversion of any biomass orits fermentation to biofuels. Examples of deleterious materials includeferrous metals, non-ferrous and heavy metals, grit, dirt, dyes,plastics, clays, gypsum, solvents, pesticides, herbicides,preservatives, paints, stains, glues, adhesives, and certain phenoliccompounds and resins, for example those present in soft wood.

The term “ethanol” refers to ethyl alcohol or mixtures of ethyl alcoholand water.

The term “cross-flow filtration cassette” refers to a type of filtermodule or filter cassette that comprises a porous filter element acrossa surface of which the liquid medium to be filtered is flowed in atangential flow fashion, for permeation through the filter element ofselected component(s) of the liquid medium. In a cross-flow filter, theshear force exerted on the filter element (separation membrane surface)by the flow of the liquid medium serves to oppose accumulation of solidson the surface of the filter element. Cross-flow filters includemicrofiltration, ultrafiltration, and nanofiltration systems. Thecross-flow filter may comprise a multiplicity of filter sheets(filtration membranes) in an operative stacked arrangement, e.g.,wherein filter sheets alternate with permeate and retentate sheets, andas a liquid to be filtered flows across the filter sheets, impermeatespecies, e.g. solids or high-molecular-weight species of diameter largerthan the filter sheet's pore size, are retained and enter the retentateflow, and the liquid along with any permeate species diffuse through thefilter sheet and enter the permeate flow. In the practice of the presentinvention, cross-flow filtration is a preferred separation method.Cross-flow filter modules and cross-flow filter cassettes useful forsuch filtration are commercially available from Smartflow Technologies,Inc. (Apex, N.C.). Suitable cross-flow filter modules and cassettes ofsuch types are variously described in the following United Statespatents: U.S. Pat. Nos. 4,867,876; 4,882,050; 5,034,124; 5,034,124;5,049,268; 5,232,589; 5,342,517; 5,593,580; and 5,868,930; thedisclosures of all of which are hereby incorporated herein by referencein their respective entireties.

The term “fermentation microorganisms” refers to any organism capable ofproducing biofuels, such as ethanol, biobutanol or lipids, such as fattyacids, for conversion to diesel. Preferred fermenting organisms for usein the present invention are ethanol-producing bacteria, yeast, algae,fungi strains or derivatives thereof. While not to be construed aslimiting, the term encompasses bacteria, such as Zymomonas mobilis andEscherichia coli; yeasts such as Saccharomyces cerevisiae or Pichiastipitis; and fungi that are natural ethanol-producers including aspecies from the genus Mortierella, Mortierrla vinacea, Mortierellaalpine, Pythium debaryanum, Mucor circinelloides, Aspergillus ochraceus,Aspergillus terreus, Pennicillium iilacinum; a species of the genusHensenulo, a species of the genus Chaetomium, a species of the genusCladosporium, a species of the genus Malbranchea, a species of the genusRhizopus, and a species of the genus Pythium. Fermentationmicroorganisms may also encompass engineered organisms that are inducedto produce ethanol or enzymes through the introduction of foreigngenetic material (such as pyruvate decarboxylase and/or alcoholdehydrogenase genes from a natural ethanol producer; exogenous sucroseutilization gene, such as a sucrose transporter, a sucrose invertase, ahexokinase, a glucokinase, or a fructokinase; a lipid pathway enzyme,such as a stearoyl-ACP desaturase, a glycerolipid desaturase, a pyruvatedehydrogenase, an acetyl-CoA carboxylase, an acyl carrier protein, and aglycerol-3 phosphate acyltransferase.). The term further encompassesmutants and derivatives, such as those produced by known genetic and/orrecombinant techniques, of ethanol-producing organisms, which mutantsand derivatives have been produced and/or selected on the basis ofenhanced and/or altered ethanol production. Bacterial strains mayinclude thermophilic bacteria including phototrophic bacteria (i.e., thepurple bacteria, green bacteria, and cyanobacteria), bacteria (i.e.,Bacillus, Clostridium, Thiobacillus, Desulfotomaculum, Thermus, Lacticacid bacteria, Actinomycetes, Spirochetes, and numerous other genera).Many hyperthermophiles are archaea (i.e., Pyrococcus, Thermococcus,Thermotoga, Sulfolobus, and some methanogens). There are aerobic as wellas anaerobic thermophilic organisms. Thus, the environments in whichthermophiles may be isolated vary greatly, although all of theseorganisms are isolated from areas associated with high temperatures.

The term “an oleaginous yeast” refers to a selected microbe from thegroup consisting of Cryptococcus curvatus, Cryptococcus terricolus,Candida sp., Lipomyces starkeyi, Lipomyces lipofer, Endomycopsisvernalis, Rhodotorula glutinis, Rhodotorula gracilis, and Yarrowialipolytica.

The term “fermentable sugar” refers to oligosaccharides andmonosaccharides that can be used as a carbon source by a microorganismin a fermentation process.

The term “lignocellulosic” refers to a composition comprising bothlignin and cellulose. Lignocellulosic material may also comprisehemicellulose.

The term “saccharification” refers to the production of simple sugarsfrom complex carbohydrates.

The terms “suitable conditions to produce fermentable sugars” refers toconditions such as pH, composition of medium, and temperature underwhich saccharification enzymes are active.

The term “hydrolysis materials” refers to any material suitable for thehydrolysis of cellulose and hemicellulose to any hexose and pentosesugar, including dilute and concentrated sulfuric acid and enzymes suchas those excreted by Trichoderma reesei.

The term “municipal solid waste” refers to garbage, trash, rubbish andrefuse that are normally disposed of by the occupants of residentialdwelling units and by business, industrial and commercialestablishments, including but not limited to: paper and cardboard,plastics, food scraps, ferrous and non-ferrous metals, wood, lumber,glass, leather, grit or dirt.

The term “homogenizer,” “colloid mill” or hammer mill refers to amachine that is used to reduce the particle size of a solid insuspension in a liquid, or to reduce the droplet size of a liquidsuspended in another liquid. Preferably, this can be accomplished byapplying high levels of hydraulic shear to the process and the machineprovides a finished product that is homogeneous, has repeatableviscosity and dispersion down to one micron, and is totally consistentfrom batch-to-batch. Preferably, the colloid mill further includes apositive displacement feed pump and can handle viscous materials from1,000 CPS and up with flow rates from 0.5 up to 300 GPM.

The term “biobutanol” refers to a four carbon alcohol derived from thefermentation of biomass including simple sugars. Biobutanol has a higherenergy content that ethanol, of about 105,000 BTO/gallon versus ethanolof 84,000/BTU/gallon. Biobutanol can also be used as industrial solvent,degreasers, paint solvent, etc. The additional of biobutanol to anengine does not require special adaptation of the engine and can becombined with gasoline at a rate of 16% which is higher than ethanol.

In one particular aspect, the present invention relates to a cross-flowfiltration cassette, as shown in FIG. 1, comprising a multilaminatearray of sheet members of generally rectangular and generally planarshape with main top and bottom surfaces, wherein the sheet membersinclude in sequence in said array a first retentate sheet, a firstfilter sheet, a permeate sheet, a second filter sheet, and a secondretentate sheet, wherein each of the permeate and filter sheet membersin said array has at least one inlet basin opening 10 at one endthereof, and at least one outlet basin opening 12 at an opposite endthereof, with permeate passage openings 13 at longitudinal side marginportions of the sheet members; each of the first and second retentatesheets having at least one channel opening 8 therein, extendinglongitudinally between the inlet 10 and outlet basin 12 openings of thepermeate and filter sheets in the array, and being compression bonded toan adjacent filter sheet about peripheral end and side portions thereof,with their basin openings and permeate passage openings in register withone another and the permeate passage openings of each of the retentatesheets being circumscribingly compression bonded to the adjacent filtersheet, and with a central portion of each of the retentate sheets andadjacent filter sheets being unbonded to permit permeate contacting theretentate sheet to flow through the filter sheet to the permeate sheet;and each of the filter sheets being secured at its peripheral portionson a face thereof opposite the retentate sheet, to the permeate sheet.

The term “sheet” will denote the generally planar members of thecassette, the cassette thus comprising an assembly of permeate sheets,filter sheets, and retentate sheets, coupled to one another in suchmanner as to permit flow of the fluid to be separated through the flowchannel(s) of the device, for mass transfer involving passage of thepermeate through the filter sheets, and retention of the retentate onthe side of the filter sheet opposite the side from which the permeateemerges.

The term “compressible” in reference to the retentate sheet or otherstructural feature or sheet member of the present invention means thatsuch component or member is compressively deformable by application ofload or pressure thereon.

The above-described filtration cassette of the invention comprises a“base sequence” of elements, defined as a sequence of sheet elementsconstituting a compressible retentate sheet (hereafter designated by thesymbol “CR”), a filter sheet (hereafter designated by the symbol “F”), aforaminous permeate sheet (hereafter designated by the symbol “P”), asecond filter sheet (“F”), and a second compressible retentate sheet(“CR”), thereby providing a sequence of sheet elements, CR/F/P/F/CR.

The base sequence of sheet elements may be utilized in construction offilters comprising a plurality of filtration cassettes, wherein thecompressible retentate sheet is utilized to seal the top and bottomelements of a plurality of filtration cassettes of a sequence,comprising compressible retentate sheet “CR”, filter sheet “F”,foraminous permeate sheet P, filter sheet “F”, non-compressibleretentate sheet “R”, filter sheet “F”, foraminous permeate sheet P,filter sheet “F”, and compressible retentate sheet “CR”. An illustrativestacked cassette filter according to the invention may for examplefeature the sheet sequence CR/F/P/F/R/F/P/F/R/F/P/F/CR as shown in FIG.2, comprising a first compressible retentate sheet, two base sequencesof sheets FPFRFPF in a repetitive sequence, and a second compressibleretentate sheet. In all repetitive sequences, other than a singlecassette base sequence, the following relationship is observed: where Xis the number of filter sheets F, the quantity 0.5 X−1 is the number ofnon-compressible retentate sheets R, and the quantity 0.5 X is thenumber of foraminous permeate sheets P, with two compressible retentatesheets being utilized to seal the top and bottom extremities of theintervening sequence.

Thus, it is possible to utilize a large number of base sequencecassettes in a repetitive sequence, to provide a stacked cassette filterof the desired mass transfer area. Many configurations are possible. Itis feasible in some instances, e.g., for mass transfer studies andsystem quantitation, to utilize a single cassette comprising the basesequence CR/F/P/F/CR wherein the outermost retentate sheets in thesequence are compression-sealed at their outer faces to an end plateaccommodating removal of permeate from the permeate passage openings ofthe constituent sheet members in the cassette.

The sheets of filter material used in the cassette article of thepresent invention may be of any suitable porosity rating. As usedherein, the porosity rating of a sheet of filter material is thesmallest particle size which cannot pass through the pores of the filtermaterial. Typical porosity ratings are expressed in molecular weight(MW) and micrometer units, e.g., a 2 micron filter media sheet being amaterial which will pass particles smaller than 2 microns in diameterthrough the pores of the material, while particles larger than 2 micronswill not be passed through the filter material, and as a furtherexample, a 10,000 MW filter media sheet being a material which will passparticles smaller than 10,000 MW in diameter through the pores of thematerial, while particles larger than 10,000 MW will not be passedthrough the filter material.

In one preferred embodiment of the cassette article of the presentinvention, a retentate sheet is provided with a plurality oftransversely spaced-apart, longitudinally extending ribs or partitions,extending upwardly from (the central portion of) each of the main topand bottom faces of the retentate sheet, such ribs or partitions beingof substantially the same height and substantially parallel to oneanother to define a series of channels between the partitions, extendinglongitudinally between the respective basin openings of the retentatesheet, on both faces thereof. The adjacent filter sheets may be furtherbonded to the outer extremities of the ribs or partitions, and the ribsor partitions may be formed of any suitable material, e.g., a flexibleresilient adhesive bonding medium, such as a urethanes, epoxy orsilicone adhesive sealant medium, e.g., applied in a “bead” in thelongitudinal direction of the retentate sheet on both main top andbottom faces thereof.

The term “bonded” in reference to adjacent sheets in the multilaminatecassette means that the adjacent sheets are secured to one another insuch manner as to prevent flow of the material being processed, e.g.,the feed material to be separated, as well as component materialstherefrom (filtrate or permeate, as well as retentate), from flowingthrough such secured areas or between the adjacent sheets at suchsecured areas. Preferably, the bonding is carried out by compressivebonding or with a suitable adhesive or sealant medium, e.g., a urethane,epoxy, cyanoacrylate, or silicone adhesive material, which fills theinterstices of the foraminous sheet in the bonded pair of sheets, andadhesively joins one of the adjacent sheets to the other in the bondedareas.

The term “compressive bonding” and “compressively bonded” refer tobonding and bonding operations in which the structure being bonded issubjected to a compressive load or force, for sufficient time and undersufficient period to effect the bonding securement of the structure.Compressive bonding of laminae in the practice of the invention ishighly desirable, in order to assure the leak-tightness and structuralintegrity of the resulting multilaminate assembly of the cassette.

The invention may for example be carried out with bonding of sheets inthe multilaminate array to one another with cyanoacrylate or other“fast” adhesives, or alternatively the adhesive or sealant medium mayrequire extended cure at ambient temperature or other appropriate cureconditions, and it may be advantageous to conduct such cure with thelaminate structure in a fixture or other assembly in which thecompressive bonding is effectively completed.

In a specific aspect of the invention, each of the foraminous permeatesheets may constitute a foraminous material of from about 80 to about300 mesh size. Each of the foraminous permeate sheets may for examplecomprise a woven polymeric mesh, e.g., of a material selected from thegroup consisting of polyester, polypropylene, nylon, fluorocarbonpolymers such as polytetrafluoroethylene, polyethylene, and polysulfone,and composites comprising one or more of such materials.

The filter sheets used in the filtration cassette of the presentinvention may be of any suitable materials, such as a material selectedfrom the group consisting of cellulose, polyphenylene oxide,polysulfone, cellulose nitrate, cellulose acetate, regeneratedcellulose, polyether amide, polyphenylene oxide/polysulfone blends,mixed esters of cellulose, and polyether sulfone.

Furthermore, it is possible to optimize the separate processes withcross-flow filtration modules of variable channel velocities but ofuniform channel heights, given the fact that most commercial cross-flowmodules are only available in a single channel height. When the channelheight of a cross-flow filtration module is known, shear is directlyproportional to channel velocity of such module for the same solutionpassing by.

In the literature, numerous techniques have been proposed to effect theseparation of target substances using membrane separations with additionof foreign substances such as acid, base, salt and solvents. In contrastto these chemical additives-based methods, the methodology of thepresent invention permits a target substance to be separated from aninput fluid by the simplest mechanical means. In the use of cross-flowfiltration modules of the type described in the aforementioned patents,the specificity and speed of a desired separation is effected by a)fluid distribution in the cross-flow module, b) channel height of thecross flow module, c) channel length, d) shear rate, e) membrane porestructure, f) membrane structure, g) membrane chemistry, h)trans-membrane pressure, and i) pressure drop, which is a function ofchannel length, velocity and solution viscosity.

The approaches by others involving various additives and manipulationsof transmembrane pressure appear to be predicated on overcoming problemscreated by poor distribution of flow within the cross-flow module. It isnot to say that the addition of salts and solvents do not have a placein separation but without proper flow distribution the membraneseparation cannot be optimally operated nor will cleaning techniques befully beneficial. It will be appreciated, based on the disclosure hereinthat numerous heretofore expensive or difficult separations are renderedfar simpler and more economical by employing the techniques describedherein.

Thus, the invention relates in another aspect to optimizing the membraneseparation process, comprising:

-   -   selecting a cross-flow membrane module wherein the distance from        the inlet port to the outlet port is equidistant from the inlet        to outlet for each sub-channel of the device, i.e., each        sub-channel is of a same dimensional character;    -   selecting an optimal channel height;    -   selecting an optimal shear rate and/or channel velocity;    -   selecting an optimal transmembrane pressure;    -   selecting an optimal membrane pore size;    -   selecting an optimal temperature;    -   selecting an optimal channel length; and    -   selecting an optimal pressure drop which is the composite of        -   the optimal channel height;        -   the optimal shear rate and/or channel velocity;        -   optimal channel length; and        -   the viscosity of the solution being filtered.

Selecting a channel height can be performed mathematically orempirically by trial and error. In most cell fermentation applications,trial and error has been more appropriate due to the fact that theviscosity of the cell broth or product solution is rarely known, thecell count and cell viability are highly variable, and the solution isfrequently non-Newtonian. The objective of channel selection is tominimize channel height with three critical stipulations: first, thechannel must be sufficiently high to allow the unrestricted passage ofany larger material such as clumped cells; second, the channel shouldnot cause excessive pressure drop and loss of linear efficiency; andthird, the channel should be sufficiently high as to allow the properangle of attack for substances to encounter the membrane pore and passthrough the pore. The optimal channel height is dependent on the lengthand viscosity of the solution.

Several notable observations have been made in initial trials andprocess scale-up, as discussed below.

For suspensions having an optical density (OD) of 2 to 500, and a pathlength of 6 to 12 inches, start with a channel height between 0.4 to0.75 mm. If the inlet pressure is above 15 PSIG at a velocity of 2.0M/sec, then the channel is too thin.

For suspensions having an optical density (OD) of 2 to 500, and a pathlength of 6 to 12 inches, start with a channel height between 0.4 to0.75 mm. If the inlet pressure is below 5 PSIG at a velocity of 2.0M/sec the channel is too high.

For suspensions having an optical density (OD) of 2 to 500, and a pathlength of 25 to 40 inches, start with a channel height between 0.7 to1.0 mm. If the inlet pressure is above 15 PSIG at a velocity of 2.0M/sec, the channel is too thin.

For suspensions having an optical density (OD) of 2 to 500, and a pathlength of 25 to 40 inches, start with a channel height between 0.7 to1.0 mm. If the inlet pressure is below 5 PSIG at a velocity of 2.0M/sec, the channel is too high.

Another aspect of the present invention relates to a stacked cassettecross-flow filter comprising cassette articles of the type describedabove.

Still another aspect of the present invention relates to a pair of endplates or manifold assembly in which the cassettes are secured foroperation as shown in FIG. 2.

Referring to FIG. 3, a reactor vessel 14 is shown in which incomingbiomass may be at least partially processed into a target product, suchas renewal fuel and fermentation microorganisms may be recovered andreturned to after separation through the cross-flow filtration cassette18 Although FIG. 3 shows only one reactor vessel, the actual number ofreactor vessels that may be incorporated into system is unlimited andreactor vessels may be added in series or in parallel, to accommodateindividual needs and production goals.

Reactor vessel sizes of 200 gallons to 50,000 gallons are envisioned foradvantageous use, although smaller or larger vessel sizes may be used.While it is envisioned that processing stoppage and cleaning betweencontinuous processing runs will be required, it is currently envisionedthat continuous processing runs of two weeks or more may be permissible.

In the reactor vessel 14, the biomass may be a carbohydrate agriculturalproduct, or byproduct. In general where the target product is ethanol,the higher the carbohydrate percentage of the biomass, the greater thepotential production of ethanol where other factors are constant. Thebiomass for use with the process invention may include a number ofstarch-, sugar- and cellulosic-based products and by-products. Asnon-limiting examples, starch-based substrates which may be usedinclude, but are not limited to: lactose, whey, whey permeate, corn,wheat, rye, rice, potatoes, and artichokes. Sugar-based substrates whichmay be used include, but are not limited to: sugar beets, sugarcane, andfruits. Cellulosic-based substrates which may be used include, but arenot limited to: wood by-products, wood fiber, plant fiber, paper andvarious grasses (e.g., prairie grass), as some examples.

Some different considerations come into play if different substrates areused. For example, if cellulosic-based biomass is used, a two-stepprocess is necessary, as the cellulosic material will first be convertedinto sugar, and the sugar will then be fermented into alcohol. These twosteps may occur in the same reactor vessel, or may be caused to occur inconsecutive, different vessels.

Chemical stabilization of the fermentation process may be enhanced byintroducing sterilizing chemicals to the biomass to exclude organismsthat may compete with the desired fermentation microbe. Sterilizingchemicals may include, but are not limited to, hydrogen peroxide andsodium sulfite. The stabilizing chemicals may be introduced prior to thefirst reactor and/or into any or all bioreactors individually orcollectively prior to, or during, the fermentation process.

In some embodiments, fermentation microorganisms may be added when thereactor vessel is 10% full with biomass. Oxygen, or gas or fluidcontaining oxygen, may be introduced to the reactor vessel. In onepreferred embodiment, after loading the reactor vessel and duringoperation of the system, a portion of the content of the reactor, thatbeing, the biomass may be continuously removed from the reactor, movedthrough the cross-flow filtration cassette, and portions are returned tothe reactor vessel. In other embodiments, the biomass may beperiodically and/or intermittently removed from the reactor vessel,moved through the cross-flow filtration cassette, and returned to thebioreactor. In some embodiments the process of removing a portion of thebiomass may commence after the reactor vessel is about 75% full withbiomass.

A portion of the contents of reactor vessel is removed from the reactorvessel and is introduced, via line 16, to the cross-flow filtrationcassette 18 wherein the biomass is separated into a retentate and apermeate. The retentate is returned to the reactor vessel via processline 22 and the permeate is introduced to the permeate vessel 20.

The components of the cross-flow filtration cassette 18 are described inFIG. 1 and relates to the separation of a target molecule, such as arenewal fuel molecule, and the separation is facilitated by the use of afiltration cassette comprising a multilaminate array of sheet members ofgenerally rectangular and generally planar shape with main top andbottom surfaces, wherein the sheet members include:

-   -   a first compressible retentate sheet of suitable material, e.g.        polysulfone, polyethersulfone, polycarbonate, urethane,        silicone, or other compressible material of construction,        having (i) at least one longitudinally extending rib or        partition element 6, such partition element(s) when provided in        multiple configuration being transversely spaced apart from one        another and being of substantially the same height and        substantially parallel to one another to define a single or a        series of channels 8 between the partitions, extending        longitudinally between the respective inlet 10 and outlet 12        basin openings of associated filter elements and permeate sheet        members, on both faces thereof, (ii) permeate passage openings        13 at side portions of the sheets, and (iii) the retentate sheet        aligned to the first sheet of filter material at respective end        and side portions thereof, with the basin openings and permeate        passage openings of the associated sheet members in register        with one another and the permeate passage opening of the        retentate sheet member being circumscribingly compressed to the        first sheet of filter material, and with a central portion of        the first sheet of filter material and the retentate sheet        member being unbonded to permit permeate contacting the        retentate sheet member to flow through the first sheet member of        filter material to the foraminous permeate sheet member;    -   a first sheet member of filter material having (i) multiple        basin openings, of a suitable shape, e.g., polygonal,        semicircular, or sector shape, at each of opposite end portions        of the sheet member defining respective inlet 10 and outlet 12        passages, each basin being bounded by generally linear side        edges defining corners of the basin at respective intersections        of the side edges, and (ii) permeate passage openings 13 at the        side portions of the sheet member, wherein the first sheet        member of filter material is bonded to the foraminous permeate        sheet member at their respective end and side portions, with        their basin openings and permeate passage openings in register        with one another and the basin openings being circumscribingly        bonded at respective end portions of the first sheet member of        filter material and the foraminous permeate sheet member, and        with a central portion of the first sheet member of filter        material and the foraminous permeate sheet member being unbonded        so as to define a central portion permeate channel of the        foraminous permeate sheet communicating with the permeate        passages in the first sheet member of filter material and in the        foraminous permeate sheet member;    -   a forminous permeate sheet member of screen or mesh material,        having (i) multiple basin openings of suitable shape at each of        opposite end portions of the sheet member defining respective        inlet 10 and outlet 12 passages, each basin being bounded by        generally linear side edges defining corners of the basin at        respective intersections of the side edges, and (ii) permeate        passage openings 13 at the side portions of the sheet member;    -   a second sheet member of filter material having (i) multiple        basin openings at each of opposite end portions of the sheet        member defining respective inlet 10 and outlet 12 passages, each        basin being bounded by generally linear side edges defining        corners of the basin at respective intersections of the side        edges, and (ii) permeate passage openings 13 at the side        portions of the sheet member, wherein the second sheet member of        filter material is compression sealed to the retentate sheet        member at their respective end and side portions, with their        basin openings and permeate passage openings in register with        one another and the permeate passage opening of the retentate        sheet member being compression sealed to the second sheet member        of filter material, and with a central portion of the second        sheet member of filter material and the retentate sheet member        being unbonded to permit permeate contacting the retentate sheet        member to flow through the second sheet member of filter        material; and    -   a second compressible retentate sheet member of suitable        material, e.g. polysulfone, polyethersulfone, polycarbonate,        urethane, silicone, having (i) at least one longitudinally        extending rib or partition element 6, provided that when        multiple partition elements are employed, the partition elements        are transversely spaced-apart from one another, such partition        elements being of substantially the same height and        substantially parallel to one another, to define a single        channel 8 or a series of channels between the partitions,        extending longitudinally between the respective inlet and outlet        basin openings of the filter elements and permeate sheet        members, on both faces thereof, (ii) permeate passage openings        13 at the side portions of the sheet member, and (iii) the        retentate sheet compression sealed to the second sheet of filter        material at respective end and side portions thereof, with their        basin openings and permeate passage openings in register with        one another and the permeate passage opening of the retentate        sheet member being compression sealed to the second sheet member        of filter material, and with a central portion of the first        sheet member of filter material and the retentate sheet member        being unbonded to permit permeate contacting the retentate sheet        member to flow through the second sheet member of filter        material to the foraminous permeate sheet member.

In operation, the cross-flow filtration cassette provides a barrierthrough which microorganisms are substantially restricted from passingthrough the filter sheets and allows microorganism concentration to beincreased and maintained at optimal levels in the reactor vessel. Thisenables microorganism concentrations to be restricted for controlled,and/or optimum, rate of conversion of substrate to target product.

After passing through the cross-flow filtration cassette, the permeatepreferably does not include microorganisms to an extent significantenough to hinder any further separation of the ethanol from thepermeate. The first retentate, which is returned to reactor vessel maystill include some of the target product (ethanol), biomass which wasnot previously converted into ethanol, unconverted sugars and/orstarches, microorganisms including the fermentation microorganisms, andother non-substrate nutrients.

In the event the fermentation microorganism cell mass in the reactorvessel exceeds a desirable level, instead of returning all of the firstretentate back to the reactor vessel, a portion of the first retentate,including the fermentation microorganism cell mass, may be bled off to asecond cross-flow filtration cassette for separating the microorganismsfrom the other components of the retentate.

In operation, after the reactor vessel receives a fermentationmicroorganism, such as yeast, and a biomass and the fermentationmicroorganism begins processing the substrate to yield the ethanol andpossible byproducts such as carbon dioxide, low molecular weightorganics, and some minerals and/or salts. Oxygen and other nutrients canbe added. In the case of ethanol, oxygen may be limited to allowanaerobic production of ethanol from yeast. Temperature in reactorvessel may also be controlled and monitored. In the case of ethanolproduction, the temperature is generally maintained at a range fromabout 25° C. to about 45° C. Agitation of the contents of the reactorvessel may be achieved through mechanical agitation devices known in theart.

FIG. 4 shows an alternative set-up for extraction of ethanol. Thissystem includes a colloid mill 26 to provide for reduction of particlesize of the corn source material 24 or any other sugar or cellulosecontaining material. The colloid mill has the ability to grind the cornto manageable sizes and easier removal of desired products. Althoughthis system shows yellow corn, other materials may be used such as cornstalks, tree material, plant material, cellulose waste, etc. Optionally,certain valuable products may be removed before forwarding to thefermentation vessel 30, such as the whole germ from the corn kernelwherein such extracted whole germ can be used in an extraction processfor the removal of corn oil. The ground material is introduced into thefermentation vessel 30 along with necessary microbes for conversion ofsugar molecules to ethanol and/or enzymes to break complex celluloseinto simple sugars such as glucose and followed by fermentation andsubsequent distillation in a distillation column 32. The bottom layer inthe distillation column is directed to a cross-flow filtration cassette34 of the present invention for separation of solids and providing for athin n which can be further separated to remove proteins and othercomponents. Any remaining wet paste may be used as animal feed.

FIG. 5 provides for a system used in dry-grain ethanol productionwherein whole grain is processed in a hammer 41 and the colloid mill 42and introduced into a liquification tank 44 for breakdown of anylignocellulose type products. Lignocellulose is a structural materialthat comprises much of the mass of plants and composed mainly ofcellulose, hemicellulose and lignin. Corn stover, switchgrass,miscanthus, wine pomace, sugarcane bagasse, municipal solid waste,woodchips and the byproducts of lawn and tree maintenance are some ofthe more popular cellulosic materials for ethanol production. Productionof ethanol from lignocellulose has the advantage of abundant and diverseraw material compared to sources like corn and cane sugars, but requiresa greater amount of processing to make the sugar monomers available tothe microorganisms that are typically used to produce ethanol byfermentation. Enzymes such as cellulase, xylanase, and hemicellulase canbe used to convert agricultural residues such as corn stover, distillergrains, wheat straw and sugar cane bagasse and energy crops such asswitch grass into fermentable sugars which may be used to producecellulosic ethanol. The contents of the liquification tank is passedthrough the cross-flow filtration cassette of the present invention 46,wherein hydrolyzates, such as proteins 47 and lignins 48 are removed andthe remaining contents moved into the fermentation vessel for theenzymatic production of ethanol. The high energy lignin and proteins canbe directed to other uses, including proteins to animal feed, yeast toother markets and the lignin can be used to replace petroleumrequirements. The ethanol containing stream is introduced to adistillation column as shown in FIG. 4, wherein the ethanol is drawn offand the remaining solution can be reintroduced into the fermentationvessel or proceed for further processing. Importantly, the setback isfree of solids, proteins and microbial contamination. Further, byremoving all solids in the setback there is more room available foradditional processed corn thereby increasing a continuous stream ofproduct. With the particle size of the feedstock reduced to less thanabout 0.5 mm all the distiller grains can be concentrated to greaterthan about 30% solids. Thus, there is less need for centrifuge orevaporation to produce grain with less moisture. The system can beoperated in both a batch and continuous mode.

Placing reactor vessels and the cross-flow filtration cassettes inseries or in parallel allows for optimal rates of substrate fermentationwhile permitting the minimization of total bioreactor size and the timerequired for production of the target product. The individual reactorvessels may be configured to operate at different fermentation cell massconcentrations or in different modes. For example, FIG. 6 showsdownstream fermentation, distillation and recovery and also showsmultiple fermentation vessels 60, 62 and 64 that can be used in thecontinuous biofuel production. Each vessel can be in a different mode,for example, one can be filling, one can be in the fermenting mode, andone can be emptying and resetting for the next batch. Further, as thefermentation medium is passed from one vessel to another, theconcentration can be reduced by use of ultrafiltration membranes betweenthe vessels. The fermentation medium, after passing through all thevessels, is passed through at least one cross-flow filtration cassetteof the present invention 66 wherein the ethanol containing liquid isintroduced to a distillation column 68 and wherein the ethanol is drawnoff through a sieve 70. The remaining effluent solution 72 can bereintroduced into the fermentation vessel or proceed for furtherprocessing, such as processing of corn steep liquor or stillage.

Corn steep liquor is one of the byproducts of corn wet milling directedto the production of animal feed. It is also used as a nutrient formicroorganisms in the production of enzymes, antibiotics, and otherfermentation products. Corn steep liquor is a source of solubleproteins, amino acids, carbohydrates, organic acids, vitamins, andminerals and can be used as a source material. Importantly, corn steepliquor is highly viscous material but using the cross-flow filtrationcassette of the present invention eliminates the need for centrifuge andtraditional filtration. Other traditional filtration membranes, such asturbulence inducing screen channels cannot handle the processing of suchthick solutions. The corn steep liquor can contain from about 15% to 25%solids and removal of liquid causes a wet distiller grain, also called awet cake that contains from about 35% to 50% weight of solids.

FIG. 7 shows a system used for both upstream and downstream processing,wherein large particles from a feed stock 80 are reduced in any particlereduction system 82, thereby providing for a fairly consistent sourcematerial for further processing. Importantly the pump system 84 from theparticle reduction system can be used as the primary pump mechanism formoving the source material through the cross-flow filtration cassette86. The cross-flow filtration cassette provides for a permeate that issolid free but still contains the necessary nutrients for a fermentationprocess when supplied to the fermentation vessel 88. Thus, the nutrientsadded to the fermentor, which are free of solids, provides forincreasing volumetric capacity by about 15 to 20%.

Ethanol producers are considering the use of corn stillage, a by-productof ethanol production, to generate renewable energy to offset fossilfuel cost and reduce the carbon intensity of the ethanol process. FIG. 6shows that the at the bottom of the distillation column 68, any solidsare removed including grain and added yeast as well as liquid addedduring the process. The thin stillage can be rerouted to thefermentation tank as make-up waste along line 72. In the presentinvention, it is envisioned that the thin stillage is concentrated bypassing through a cross-flow filtration cassette of the presentinvention wherein additional water is removed thereby forming aconcentrated stillage without the need of an evaporator. Theconcentrated syrup with a content of 30% to 60% of solids and which ishigh in proteins can be used either as a component in wet distillergrain for feeding to cattle or can be used as a feedstock in biogasproduction. For example, the thickened syrup may be added to a digesterand produces methane. Interestingly, this methane gas can be used topower the ethanol process.

FIG. 8 shows that using the cross-flow filtration cassette forconcentrating the thin stillage cut provides for at least twice theamount of solids in the stillage and providing for increasedconcentration. As viewed in FIG. 8, the syrup with 32% solids showed anincrease in solidity and no drainage on the vertical slab. This is incomparison to the thin stillage that passed through an evaporator andcontained only 16% solids which means that it still include 86% liquid.Importantly, this increase in concentration provides for a higher valuecompound whether used in a biogas setup or feed to cattle.

Biogas systems may also use the cross-flow filtration cassettes of thepresent invention. Many farmer use methane digester to process farmwaste, such as that involved with grain crops, seed, leaves, plants anddry or wet manure. The farm waste is processed in anaerobic digesters toderive methane biogas. The biogas is captured and the remaining biowaste(usually referred to as sludge and containing numerous nutrients) can befurther concentrated by use of the cross-flow filtration cassettes ofthe present invention and then further processed for production ofadditional biofuels, such as ethanol and biobutanol. Nutrients can beremoved including ammonia, phosphorus, potassium and other traceelements by use of the cross-flow filtration cassettes and that can beadded to animal feed or reintroduced to soil as nutrients.

FIG. 9 illustrates the steps for converting lignocellulose-to-ethanol.Initially, the biomass may be subjected to size reduction 90 by millingor chipping and the opening of the fibrous material for furthertreatment. The next step includes the pretreatment 92 for mobilizationof the lignin and hemicellulose biopolymers. Sugars are collected eitherdirectly or from further breakage for enzymatic attack by hydrolysis ofthe polysaccharide matrix 94 to a sugar stream. The sugar stream can beconcentrated by evaporation 96 to a level sufficient for a final ethanolconcentration of at least 8.5%. The concentrated sugar material isfermented 98 and then subjected to further distillation and purificationsteps 100 to meet fuel specifications. The bottoms of the distillationprocess 102 are removed for further processing to provide additionaldesired products. All of the separation or purification processes usethe cross-flow filtration cassettes 91 of the present invention.

That which is claimed is:
 1. A method of producing a renewable fuelmolecule from corn grain, the method comprising: (a) providing corngrain and introducing same into a particle reduction system to provide amixture of corn particles; (b) introducing the mixture of corn particlesto a liquification tank comprising a liquid medium, under heat, torelease starch granules from the corn particles; (c) introducing enzymesto the liquid medium for break down of the starch granules into simplesugars; (d) moving the liquid medium comprising the simple sugars into afermentation vessel along with a fermentation microorganism forconversion of the simple sugars to the renewable fuel molecule; (e)moving the liquid medium comprising the renewable fuel molecule into adistillation column for extraction of the renewable fuel moleculetherefrom; and (f) moving the remaining liquid medium comprisingresidual water and corn solids through a cross-flow filtration cassette,wherein an amount of water is removed and the remaining syrup can beused as a component of animal feed.
 2. The method of claim 1, whereinthe mixture of corn particles of step (b) is separated from the starchgranules by passing the liquid medium comprising the starch granules andcorn particles through a cross-flow filtration cassette, wherein thecross-flow filtration cassette comprises: an array of sheet members ofgenerally rectangular and generally planar shape with main top andbottom surfaces, wherein the sheet members include in sequence in saidarray a first retentate sheet, a first filter sheet, a permeate sheet, asecond filter sheet, and a second retentate sheet, wherein a medium tobe filtered flows across the filter sheets, solids orhigh-molecular-weight species of diameter larger than the filter sheet'spore size, are retained in the retentate flow, and at least a portion ofthe liquid medium with any permeate species diffuses through the filtersheets and enters the permeate sheet and permeate flow; wherein each ofthe sheet members in said array has at least one inlet basin opening atone end thereof, and at least one outlet basin opening at an oppositeend thereof, with permeate passage openings at longitudinal side marginportions of the sheet members, wherein each of the first and secondretentate sheets having a multiplicity of channel openings therein,extending longitudinally between the inlet and outlet basin openings ofthe sheets in the array, and being bonded to an adjacent filter sheetabout peripheral end and side portions thereof, with their basinopenings and permeate passage openings in register with one another andthe permeate passage openings of each of the retentate sheets beingcircumscribingly bonded to the adjacent filter sheet, and with a centralportion of each of the retentate sheets and adjacent filter sheets beingunbonded to permit permeate contacting the retentate sheet to flowthrough the filter sheet to the permeate sheet.
 3. The method of claim1, wherein the renewable fuel molecule comprises ethanol.
 4. The methodof claim 1, wherein the simple sugars comprise at least one of glucose,xylose, arabinose, maltose or galactose.
 5. The method of claim 1,wherein the particle reduction system comprises a colloid mill.
 6. Themethod of claim 1, wherein the cross-flow filtration cassette comprisesan array of sheet members of generally rectangular and generally planarshape with main top and bottom surfaces, wherein the sheet membersinclude in sequence in said array a first retentate sheet, a firstfilter sheet, a permeate sheet, a second filter sheet, and a secondretentate sheet, wherein a medium to be filtered flows across the filtersheets, solids or high-molecular-weight species of diameter larger thanthe filter sheet's pore size, are retained in the retentate flow, and atleast a portion of the liquid medium with any permeate species diffusesthrough the filter sheets and enters the permeate sheet and permeateflow; wherein each of the sheet members in said array has at least oneinlet basin opening at one end thereof, and at least one outlet basinopening at an opposite end thereof, with permeate passage openings atlongitudinal side margin portions of the sheet members, wherein each ofthe first and second retentate sheets having a multiplicity of channelopenings therein, extending longitudinally between the inlet and outletbasin openings of the sheets in the array, and being bonded to anadjacent filter sheet about peripheral end and side portions thereof,with their basin openings and permeate passage openings in register withone another and the permeate passage openings of each of the retentatesheets being circumscribingly bonded to the adjacent filter sheet, andwith a central portion of each of the retentate sheets and adjacentfilter sheets being unbonded to permit permeate contacting the retentatesheet to flow through the filter sheet to the permeate sheet.